Acidification of target water with H2SO4 in a specially constructed glassy carbon/polyethylene apparatus allowed for recovery of up to 82% of [18F]fluoride as [18F]HF gas. The [18F]HF distillate was found to be acid-free but moist; when passed through a solution of tBuPh2SiOTf, it yielded [18F]tBuPh2SiF. The multivariate design of experiment showed that the key to high yield of [18F]HF was the efficient degassing of the reaction mixture.